The present disclosure relates to assays for detecting or quantifying the concentration of large and small molecules in biological fluids. The disclosure also relates to devices used in such assays and methods for making and using them.
Many types of large and small molecules can be detected in biological fluids. Such molecules may include enzymes, viruses, proteins, hormones, antibodies, antigens, and various biological waste products. For example, some specific molecules include human chorionic gonadotropin, ICAM, VCAM, integrin, fibrin, and prostate-specific antigen (PSA). As another example, troponin is a complex of three proteins that is integral to muscle contraction in skeletal and cardiac muscle, but not smooth muscle. Those three proteins, also called subunits, are known as troponin C, T, and I. The troponin of skeletal and cardiac muscle can also be differentiated from each other. One difference is that the troponin C subunit of troponin in skeletal muscle has four calcium ion binding sites, whereas in cardiac muscle there are only three.
Cardiac troponin I and T are very sensitive and specific indicators of damage to the heart muscle (myocardium). They are measured in the blood to differentiate between unstable angina and myocardial infarction (heart attack) in patients with chest pain. In particular, elevated levels of troponin in the blood is an indicator of damaged heart muscle.
Heart disease is a leading cause of death in the United States. The American Heart Association has estimated that 1.2 million people suffer a heart attack every year and that 40% of them die as a result.
Immediate treatment of a heart attack is important to preserve heart muscle and minimize damage and other long-term consequences to the patient. For example, some treatment therapies can only be administered within certain time windows from onset of symptoms. In addition, some treatments which are given for a heart attack are inappropriate and possibly adverse if the patient turns out to be suffering from something else. It would be desirable to have an assay that can detect the presence of troponin and/or other cardiac markers quickly to confirm the diagnosis of a heart attack.
In another aspect, hepatitis C virus (HCV) is a blood-borne virus. Once a person is chronically infected, the virus is almost never cleared without treatment and HCV is a major cause of chronic hepatitis. Some go on to develop cirrhosis and end-stage liver disease. It would be desirable to be able to test for viruses such as HCV.
Accordingly, the need exists for a relatively rapid device for detecting the presence and/or amount of molecules in biological fluids.